These sensors, referred to using the term geophones, are generally interconnected in groups of sensors by cables to form clusters referred to as “strings”. One or a plurality of these strings are connected to the electronic units.
In order to collect the geophysical data, one or a plurality of seismic sources in contact with the ground are activated to propagate omnidirectional seismic wave trains, which are reflected by the layers of the subsurface, and detected by the sensors. The sensors generate a digital or an analogue signal characterising the reflection of the waves on the geological interfaces of the subsurface, which is sent to the electronic units.
When sensors are analogue, the electronic units perform the analogue to digital conversion (ADC) of the signal from the groups of sensors.
The electronic units then send the data with the signals to a central data processing unit, which may be on-board a truck or boat, via possibly other electronic modules like concentrators, all parts of a cabled digital network.
Land seismic operations take place in different zones:                dry areas, with very low tensile stress, and for which the equipment including cables and electronic modules is required to have a water-tightness down to 1 m deep;        marsh areas, with low tensile stress and for which the equipment is required to have a high robustness and a water-tightness down to 5 m deep;        shallow water areas, with high tensile stress and bending stress, and for which the equipment is required to have high robustness and water-tightness up to 15 m deep.            Both marsh and shallow water areas are often referred to as transition areas.
Geophysical equipment is used in dry areas for about 95% of the land operations.
Each cable of the cabled system, or geophysical equipment, has several connectors for connecting portions of cables one to another. In case of getting through a transition area during a land operation, the connectors should be protected from tensile stress.
It is known, as a state of the art, to add a rope for joining together two points of a cable on each side of a connector, so that the length of the rope is shorter than the distance between the two points along the cable and the connector. Such a system of ropes creates a diversion for tensile stress through the rope, creating a stress relief in the connector and therefore protecting it.
A drawback of such a system with ropes is that the loop formed by the rope and the connector, which is quite big, might be hooked for example by underwater debris inducing tension. In such a case, the corresponding bending and/or tensile stress may then be communicated to the connector itself, then subject to more stresses than without any loop.
Furthermore, when retrieving the equipment on-board a ship or truck, the connectors can get stuck on an edge, producing a significant lever arm inducing bending on the connecting assembly. This stress is of particular severity for the connectors for which the state of the art with ropes is of no help.
Since a connector is rarely used in a transition area, the added constraint for the connector due to the ropes is not balanced by advantage most of the time.